Conventionally, wireless base stations (radio base stations) in a cellular system are connected, via a wired transmission interface, to a radio network controller (RNC), an upper level apparatus, to which the wireless base stations are subordinate (or to an access gateway apparatus). The radio network controller integrally monitors and controls configuration information of each wireless base station, such as coverage area, channel accommodation capacity, and transmission power, through the wired transmission interface.
In the communication of information between wireless base stations subordinate to one radio network controller, the radio network controller is capable of monitoring and controlling configurations of the subordinate wireless base stations using the wired transmission interface in the radio network controller.
Some techniques are known that allow adjacent wireless base stations to share information held by each wireless base station. For example, one such technique is for a small-scale zone configuration and allows a user to set up a wireless base station freely in CDMA-based communication (see, e.g., Japanese Laid-Open Patent Publication No. 2007-329758). According to this technique, when a wireless base station is set up and started, processing of an uplink base band signal from a terminal is switched over to a process of receiving a signal from a common downlink channel of an another wireless base station to measure report information and signal levels of surrounding wireless base stations. Through this process, the setting of spread codes, transmission power, etc., necessary for setting up the wireless base station is carried out automatically (see, e.g., Japanese Laid-Open Patent Publication No. 2007-329758). In this configuration, the wireless base station is able to acquire the setup statuses and radio wave propagation conditions of other surrounding wireless base stations in a wireless access system, the setup statuses and propagation conditions being dependent on the place of setup.
Another technique is for building a service area by setting up wireless base stations in an OFDM system (see, e.g., Japanese Laid-Open Patent Publication No. 2008-270915). According to this technique, when a wireless base station is set up and started, processing of an uplink base band signal from a terminal is switched over to a process of receiving a downlink signal from an another wireless base station to measure working carrier wave frequency information and signal levels of surrounding wireless base stations. Through this process, the carrier wave frequency having the least interference is selected and the setting of transmission power, etc. is automatically carried out. This configuration enables acquisition of the setup statuses and radio wave propagation conditions of other surrounding wireless base stations in a wireless access system, the setup statuses and propagation conditions being dependent on the place of setup of the wireless base station.
If central monitoring and control is carried out by a radio network controller (access gateway apparatus), as in the case of the conventional techniques, wireless base stations subordinate to the radio network controller are limited in number. For this reason, when information is transmitted between wireless base stations subordinate to different radio network controllers and such wireless base stations are controlled, communication via an additional upper level apparatus is carried out, requiring a wired transmission interface between radio network controllers.
When additional wireless base stations are set up to deal with a change in a radio environment or an increase in the number of users, a wired transmission interface is newly provided between radio network controllers. The radio network controller is, however, limited in the number of wireless base stations that can be accommodated. As a result, load on the radio network controller increases, leading to complicated control processes.
According to the technique recited in Japanese Laid-Open Patent Publication No. 2007-329758, a wireless base station measures report information and the signal level of an adjacent wireless base station without communication through a radio network controller and based on this information, is able to autonomously determine configuration information in the wireless base station. Common channel power output from an adjacent wireless base station is, however, determined to be of a magnitude that causes radio waves to reach an additionally set up wireless base station. Configuration information of the adjacent wireless base station, therefore, cannot be altered automatically after setting up the additional wireless base station. As a result, radio waves output from the additionally set up wireless base station have an output power that interferes with radio waves from an adjacent wireless base station. This gives rise to a problem in that the number of users that can be accommodated by the wireless base stations decreases.
The technique disclosed in Japanese Laid-Open Patent Publication No. 2007-329758 is related to a configuration for startup of a new wireless base station and therefore, does not enable automatic adjustment of configuration information between wireless base stations adjacent to each other during actual operation. An attempt to alter the configuration information during actual operation would force communication service to come to a halt. The technique disclosed in Japanese Laid-Open Patent Publication No. 2008-270915 is implemented by applying the technique disclosed in Japanese Laid-Open Patent Publication No. 2007-329758 to an OFDM system, thus poses a problem similar to the problem related to the technique disclosed in Japanese Laid-Open Patent Publication No. 2007-329758.
In this manner, according to the conventional techniques, a wireless base station receives common channel output from an adjacent wireless base station to autonomously determine configuration information of the wireless base station. Both techniques, however, are related to actions that are taken at the startup of the wireless base stations. Because no communication is carried out between adjacent wireless base stations in actual operation following the startup, the adjacent wireless base stations are not able to share configuration information. As a result, the adjacent wireless base stations are unable to have the optimum configuration information after the start of operation. If the configuration information of each of the wireless base stations is not optimized, it is impossible to deal with a change in the radio wave environment and with fluctuations in the number of users.